MethodologyScientific basisData and methods
The UWTV survey has been conducted since 1992. Potential bias in survey design has been detected and accounted for in the assessment this year (see “Data and methods” section at the start of section 6.4.14.)Information from the fishing industry
The NSCFP stock survey shows an increase in Nephro
ps between 2001 and 2002, a slight decrease to 2003, and a marked increase up to 2007. Stock levels are considered to be similar or slightly less in 2008 (Figure 220.127.116.11). This information is broadly consistent with trends in the UWTV survey results.Uncertainties in assessment and forecast
General comments are found at the start of section 6.4.14
The UWTV survey is conducted over the main part of the ground, representing an area of around 28 200 km2
of suitable mud substrate (the largest ground in Europe). The Fladen Ground Functional Unit contains several patches of mud to the north of the ground which are fished, bringing the overall area of substrate to 30 633 km2
. This area is not surveyed but would add to the abundance estimate. The absolute abundance estimate for this ground is therefore likely to be underestimated by the current methodology.Comparison with previous assessment and advice
The perception of stock in 2008 is similar to that in 2007 from the assessment in 2008.
The advice in 2008 was based on recent landings as the UWTV surveys were considered inappropriate to use as absolute indices of abundance. Following the outcome of the benchmark in 2009, the major concerns of the UWTV survey have been addressed and the survey is now considered a reliable estimate of absolute abundance.
The landings forecast for 2010 (equivalent to fishing at F0.1
) is 16,419 tonnes. This is an increase of almost 4,000 tonnes on the reported landings in 2008.